Method for constructing a concrete floor in a multistorey building

ABSTRACT

The invention provides a method of forming a concrete floor of a multistorey building, the method including: installing a first building module having a first precast concrete floor slab adjacently spaced from a second building module having a second precast concrete floor slab, at least the first precast concrete floor slab supporting an upstanding support member for supporting an upper floor; forming a channel between the spaced first and second precast concrete floor slabs by providing supporting formwork between the floor slabs for supporting poured concrete; and pouring concrete into the channel to form a concrete connection between the first and second precast slabs, thereby forming a concrete floor of a building.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/092,808, filed Oct. 11, 2018, which is a U.S. National StageApplication of International Application No. PCT/AU2017/050546, filed onJun. 5, 2017, which claims the benefit of Australian Patent ApplicationNo. 2016902460, filed on Jun. 23, 2016, and which claims the benefit ofAustralian Patent Application No. 2016903025, filed on Aug. 1, 2016, andwhich claims the benefit of International Application No.PCT/AU2017/050063, filed Jan. 27, 2017, and which claims the benefit ofInternational Application No. PCT/AU2017/050064, filed Jan. 27, 2017,the entire disclosures of which are incorporated herein by reference forall purposes.

FIELD OF THE INVENTION

The invention relates to methods for constructing a concrete floor inmultistorey buildings.

BACKGROUND OF THE INVENTION

In the construction industry modular buildings are becoming more popularas they can be largely constructed offsite and assembled on site into afinished product in shorter timeframes than traditional multi-storeybuildings. Modular construction involves building and preparing buildingmodules offsite in a factory setting before transporting and installingthe module at an installation location. Despite the time saving benefitsof modular construction techniques there is a constant pursuit toimprove these methods of construction with the aim of achieving timesavings and cost savings in the overall construction of the building.

It is in light of these pursuits for efficiencies in current theconstruction of modular buildings that the invention was conceived.

SUMMARY OF THE INVENTION

The invention provides a method of forming a concrete floor of amultistorey building, the method including: installing a first buildingmodule having a first precast concrete floor slab adjacently spaced froma second building module having a second precast concrete floor slab, atleast the first precast concrete floor slab supporting an upstandingsupport member for supporting an upper floor; forming a channel betweenthe spaced first and second precast concrete floor slabs by providingsupporting formwork between the floor slabs for supporting pouredconcrete; and pouring concrete into the channel to form a concreteconnection between the first and second precast slabs, thereby forming aconcrete floor of a building.

An advantage of providing a method that uses concrete to connectadjacently spaced precast floor slabs, such as floor slabs in a buildingmodule, is that the step of pouring of concrete to connect the slabs canbe decoupled from the construction and assembly of the building,particularly where the building is constructed with modular buildingunits. Furthermore, the amount of formwork used with the present methodof using hybrid wet and precast components is reduced compared totraditional multilevel building methods, when that formwork is providedas a separate structure to the precast floor slabs.

In one embodiment the method includes installing a third building modulewith a third precast concrete floor slab above the first precastconcrete floor slab and supporting the third precast concrete floor slabon the upstanding support member. The method may include using atemporary support member or a permanent support member as the upstandingsupport member. The method may include using an upstanding supportmember in the form of a wall structure. The method may includeinstalling the third precast concrete floor slab before the concrete ispoured into the channel to form the concrete connection between thefirst and second precast slabs.

In another embodiment the method includes erecting formwork and pouringconcrete to form a concrete beam connecting the floor slabs, therebyforming a floor of a building having a cast concrete beam. The methodcan include installing multiple precast floor slabs and casting beamsextending between the slabs in different directions, such asperpendicular cast beams.

In another embodiment the method includes precasting the first precastconcrete floor slab to have a first portion and a second portion, athickness of the second portion being greater than a thickness of thefirst portion. The second portion may be precast to create an integrallyformed concrete beam. The integrally formed concrete beam may span alength or width of the concrete slab. The method may include pouring theconcrete to a thickness greater than the thickness the first portion ofthe first concrete floor slab. The method may further include pouringthe concrete to a thickness substantially equal to the thickness of thesecond portion of the first concrete floor slab.

In another embodiment the method includes pouring the concrete to belevel with a top surface of the first and second precast concrete floorslabs. The method may include precasting the first concrete floor slabto include a steel beam at least partially embedded into the firstprecast concrete floor slab.

The method preferably includes installing the slabs in elevation todefine an upper storey floor. In a preferred embodiment the first andsecond precast floor slabs are each formed as part of a buildingmodular, where building modules can be assembled one above the otherwith floor slabs suspended in elevation one adjacent the other.

The method may also include vertically inserting a pre-fabricatedconcrete wall panel in between the adjacently spaced precast floorslabs, erecting formwork between the precast floor slabs and pouringconcrete into the formwork to tie the vertical wall panel to the floorslabs. Installing precast slabs vertically to form a wall between floorslabs, particularly elevated floor slabs, and then tying the wall slabto the floor slabs by way of the wet joint defined by the in situ pouredconcrete, provides an efficient means of installing structural supportin a building.

The method also preferably includes post tensioning the precast floorslabs by, before pouring concrete into the channel, installing a conduitbetween bores extending through the first precast floor slab and thesecond precast floor slab to form a tensioning passage that extendsthrough both the first and second precast floor slabs;

-   -   pouring concrete into the channel between the first and second        precast concrete slabs to connect the first and second precast        slabs, thereby forming a slab of a building; and    -   feeding a tensioning cable, such as a tendon, through the        tensioning passage and tensioning the tensioning cable.

Post tensioning of the formed connection, or ‘wet joint’ once it hasdried, and the floor slabs increases the strength of the resultingconcrete floor structure by compressing the concrete slabs. It ispossible to tension the full span of a slab made from multiple precastconcrete floor slabs. Alternatively, the concrete floor can bereinforced using reinforcement bars embedded into the poured and/orprecast concrete.

The method could also include precasting any of the precast concretefloor slabs to include an integrally formed beam. For example, the firstprecast floor slab could have an integrally cast beam.

By providing a method that uses a combination of poured and precastbeams it is possible to reduce the number of slab to beam connections,which can be complex and time consuming. In addition, by providing aprecast concrete slab with integrally formed structural precast beamsthe remaining areas of the precast slab can be thinner than a slab witha constant thickness. In other words, by strengthening targeted areas ofthe precast concrete slab it is possible to reduce the overall weight ofthe slab for a given floor space. By reducing the weight for a givenfloor space the size of the precast concrete slab, or the buildingmodule that the precast concrete slab forms, can be increased whilemaintaining the same weight. This is beneficial as weight is a limitingfactor dictating the size of building modules (the building modules needto be transported and lifted into position).

The second precast concrete slab may also have an integrally formedbeam. The integrally formed beam of the second precast concrete slab maybe co-axial with the integrally formed beam of the first precastconcrete slab, when the second precast concrete slab is adjacent to thefirst precast concrete slab. Once the poured concrete beam has set theprecast beam in the first precast concrete slab and the precast beam inthe second precast concrete slab may form a single continuous beam.

The first precast concrete slab may have a second precast beam. Thesecond precast beam in the first precast concrete slab may beperpendicular to the first beam in the first precast concrete slab.

The first precast concrete slab may have a reinforcing bar or angle thatextends from the first precast concrete slab to anchor the first precastconcrete slab to the poured concrete beam.

The first precast concrete slab may form the base of a building module.The first precast concrete slab, or the building module, may be made ina first location and transported to a second location for installation.

The first precast concrete slab may form the base of a building module.The first precast concrete slab, or the building module, may be made ina first location and transported to a second location for installation.

The invention also provides a method of forming a concrete floor of amultistorey building, the method including: installing a first buildingmodule having a first precast concrete floor slab adjacently spaced froma second building module having a second precast concrete floor slab,the first precast concrete slab having a first aperture extendingthrough the first pre-cast concrete slab and the second concrete slabhaving a second aperture extending through the second pre-cast concreteslab; installing a conduit between the first aperture and the secondaperture to form a tensioning passage that extends through both thefirst and second pre-cast concrete slabs; forming a channel between thespaced first and second precast floor slabs by providing supportingformwork between the floor slabs for supporting poured concrete; andpouring concrete into the channel to form a concrete connection betweenthe first and second precast slabs, thereby forming a concrete floor ofa building.

The method may include feeding a tensioning cable through the tensioningpassage and tensioning the tensioning cable to post-tension the concretefloor.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment, incorporating all aspects of the invention, will now bedescribed by way of example only with reference to the accompanyingdrawings in which;

FIG. 1 is an isometric view of multi-storey building in which a concretefloor is being constructed in accordance with an embodiment of thepresent invention;

FIG. 2A is a plan view of a concrete floor of a building made inaccordance with an embodiment of the present invention;

FIG. 2B is a cross-sectional view of the concrete floor in FIG. 2A,taken at the line A-A;

FIG. 3A is a top isometric view of the concrete floor in FIG. 2A;

FIG. 3B is a bottom isometric view of the concrete floor in FIG. 3A;

FIG. 4A is a top isometric view of a precast concrete floor slab havingan integrally formed beam;

FIG. 4B is a bottom isometric view of the precast concrete floor slab inFIG. 4A;

FIG. 5 is a cross-sectional view of a first precast slab and a secondprecast slab joined together by an in situ concrete connection;

FIG. 6 is a zoomed out view of the view in FIG. 5 illustrating the firstprecast slab with the in situ concrete connection on one side and afaçade building edge on the other;

FIG. 7 is a cross-sectional schematic view of an alternative firstprecast slab and second precast slab joined together by an in situconcrete connection in line with a precast wall;

FIG. 8 is a cross-sectional schematic view of three precast slabsconnected together side-by-side by two in situ concrete connectionstherebetween;

FIG. 9 is an enlarged side view of a precast concrete slab similar toFIG. 8 with a precast beam and attached to a façade side of a buildingwith the precast slab positioned between precast columns;

FIG. 10(a) is an enlarged view of another embodiment of the invention;

FIG. 10(b) is a side view showing one of the concrete floor illustratedin FIG. 10(a);

FIG. 11(a) is a perspective view of a building module having a concretefloor as illustrated in FIGS. 10(a) and 10(b);

FIG. 11(b) is a perspective view of adjacently positioned buildingmodules of the type illustrated in FIG. 11(a); and

FIG. 12 is a side view similar to FIG. 10(a) illustratingdiagrammatically the channel into which concrete is to be poured.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

FIGS. 1 to 9 illustrate methods of constructing a concrete floor inmultilevel buildings with specific reference, by example, to multilevelbuildings built with modular building units, or building modules.

FIG. 1 illustrates a modular building 100, which is typically amultistorey building, made of building modules formed off site. FIG. 1illustrates a building module 20 being lowered onto the top level of themulti-storey building 100 formed from assembled modules and partly cladwith a façade 21. The transportation of each module from a firstlocation off site to the installation site and the subsequentconstruction requires the modules to maintain a certain stability sothat they can be handled by cranes and other handling equipment on andoff the transportation vehicle, and placed or stacked on site so thatthey can support other modules placed on top.

The figures illustrate building units, or modules 20, 22, 24, 26,including respectively floor slabs 10, 12, 14, 16. Specifically, thefloor slabs from adjacently spaced modules, are shown as ‘stitched’together, in other words joined together by in situ wet jointconnections of concrete. In the embodiment described, the connectionsare formed to create in situ beams for reinforcing a finished floorstructure. The in situ formed joins, preferably in the form of beams,are structural joins that contribute to the structural stability of thebuilding and therefore reduce the amount of vertical support required inthe vicinity of the beams.

The floor slabs can be arranged in any orientation. In the embodimentillustrated the floor slabs, or building modules, are arranged side byside in two directions across a building storey (i.e. installing floorslabs a single horizontal plane). This means that the concrete isapplied, by pouring or even by spraying, to create poured beamsextending in multiple directions, such as in perpendicular directions asillustrated in the drawings. Installing the next level of the modularbuilding 100 requires installing floor slabs above the already installedprecast concrete floor slabs (i.e. installing vertically).

An advantage with the presently described system and method of forming aconcrete floor of a multistorey building, and indeed the system andmethod of forming a multistorey building itself, is that the erection ofthe framework in the building, namely in the form of building units(modules), is decoupled from the process of joining the building unitstogether.

In known building systems the floor of one storey needs to be completed,or joined together, by concreting to a substantially finished statebefore the walls can be erected on that floor. Furthermore, the wallsneed to be erected before the floor of the next storey up can be erectedand supported by the walls.

In the present system and method, the framework including floor slabsand upright supports of multiple storeys can be erected in advance ofthe floors below being stitched together with concrete. This decouplingof erecting multiple storeys from concreting a floor increases buildingefficiencies and decreases building time because it is not necessary towait for a freshly poured concrete floor to dry before the next level upcan be built.

The in situ poured beams can either be tensioned by post tensioningtechniques or reinforced with reinforcing steel. Accordingly, theresulting structure includes a concrete floor strengthened by 2-waytensioned or reinforced beams.

FIGS. 2A to 3B illustrate in plan view four floor slabs, shown asprecast concrete floor slabs 10, 12, 14, 16, on a single level 18 of amultistorey building, shown as modular building 100. Each of the precastconcrete slabs 10, 12, 14, 16 forms the base of the building modules 20,22, 24, 26 respectively for the modular building. The precast concreteslabs 10, 12, 14, 16 are connected together by poured concrete 11 toform a completed floor slab 17. The term ‘poured’ is used herein but itis understood that the concrete could also be sprayed, or applied byother wet concrete techniques, to form a beam connection betweenindividual floor slabs.

The precast concrete floor slabs 10, 12, 14, 16 each have at least oneupstanding support member attached to them, where that upstandingsupport member is a permanent or temporary support with which, or onwhich, a further storey (usually another building module with a concreteslab) can be installed above the lower concrete floor slab to therebyconstruct a multi-storey building.

For example, referring to FIG. 4A, precast concrete floor slab 10 hasmultiple upstanding support members, shown as temporary support members103. The temporary support members 103 can be used to support a concretefloor above (not shown) while a wall, column or façade of floor slab 10is erected, and can also be used to assist with support in erectingpermanent vertical supports. The temporary supports are then removed aspermanent vertical support is provided by the installed wall, column orfaçade.

The precast concrete floor slabs may be described as being provided witha wall structure. It is envisaged that the wall structure could be aninternal wall, a façade wall, or a structure to allow creation of a wall(such as shutters for pouring or spraying concrete walls). As shown inFIG. 3A, the precast concrete floor slab 10 of module 20 has façadepanels, shown as windows 105. In this embodiment the facade panels 105are connected to their respective floor slabs through brackets 29 andfixing joints that are embedded into the side edges of the floor slabsduring the pre-casting process. The side section views of FIGS. 6 and 9also illustrate the facade 21 attached to the side of the precastconcrete floor slabs 40, 240. In constructing a multistorey building inaccordance with this embodiment, the entire module of floor slab andfacade, with temporary upright supports, is craned and located inposition above a storey with floor slabs below.

As an alternative to using temporary vertical/upright supports the wallstructure itself on the precast concrete floor slab may form theupstanding support member providing the vertical support required tosupport a concrete floor slab of a storey above, or indeed to supportmultiple storeys above. Further still, a combination of temporary andpermanent upstanding supports could be incorporated onto the concretewall slab, as described with the facade embodiment above.

Referring to FIG. 1 by way of explanation, the temporary support members103 act to vertically space the precast concrete floor of one level ofthe modular building 100 from another level of the modular buildingduring construction. In this way the upper concrete floor slab is heldin the correct position by the temporary support members 103 until thepermanent support members are installed on site. Thereafter thetemporary support members 103 may be removed and reused for the otherbuilding modules. It is envisaged that the aforementioned wallstructures can be the permanent support members, once they are installedand attached to the upper concrete floor slab.

In the embodiments illustrated, the precast concrete slabs each haveprecast beams integrally formed into the precast concrete slabs 10, 12,14, 16. Precast concrete slab 10 has two precast beams 32, 34. Precastconcrete slab 12 has two precast beams 33, 35. Precast concrete slab 14has one precast beam 36 32, 34. Precast concrete slab 16 has one precastbeam 37. The integrally formed beams 32, 33, 34, 35, 36, 37 extenddownwards from the precast concrete slabs 10, 12, 14, 16. The integrallyformed beams are structural beams engineered to support the load of thebuilding structure once constructed.

The term building module is intended to refer to a modular constructionor building unit that is created off site, for example in a factorysetting, and is transported on site to be assembled with other buildingmodules to construct a multi-storey building. The building module couldbe provided in a basic form comprising a base and a frame, or facade,fixed to the base that forms the ‘bones’ of walls and a ceiling.Alternatively, the building module may comprise a building unit in analmost finished state including base, walls, ceiling and even fixtures.Logically, the building module may include a construction manufacturedto a state between the basic and the almost finished forms discussedabove.

Further information regarding methods for installing a building moduleabove an existing building module (e.g. by using temporary supportmembers) can be found in co-pending International Patent Application no.PCT/AU2017/050064 titled “METHODS AND APPARATUS FOR CONSTRUCTINGMULTI-STOREY BUILDINGS”, which also claims priority from Australianprovisional application no. 2016902460 filed on 23 Jun. 2016 titled“METHODS AND APPARATUS FOR CONSTRUCTING BUILDINGS”, and from Australianprovisional application no. 2016903025 filed on 1 Aug. 2016 and titled“METHOD FOR CONSTRUCTING A CONCRETE FLOOR IN A MULTISTOREY BUILDING”.The description and teachings of that co-pending international patentapplication is incorporated herein by reference to save reproducing thatentire description herein.

Referring to FIGS. 4A and 4B, the precast concrete slab 10 of module 20is shown in greater detail. The mould that is used to create the slab 10is shaped so that the resulting slab has two beams 32, 34 integrallyformed into the slab 10. The beams 32, 34 are of greater thickness thanthe portion 11 of the slab 10 that does not have a beam. In other words,the first precast concrete floor slab has a first portion 11 and asecond portion 101, where the thickness of the second portion 101 isgreater than the thickness of the first portion 11 (i.e. creating anintegrally formed beam). The integrally formed beams 32, 34 provideadditional strength and help to reduce the number of beams that need tobe poured on site during construction, thereby reducing the amount oftime taken to pour each level of concrete at the building site. This canlead to more efficient construction times.

It is, however, understood that the method of construction does notnecessarily require the precast floor slabs to include integrally pouredbeams. The slabs may instead be planar and arranged to be stitched, ie.connected, to other slabs that may or may not have integrally formedbeams in order to provide a strong concrete floor constructed from aseries of interconnected precast concrete floor slabs.

An advantage of forming a finished concrete floor from precast floorslabs connected through wet joints is that a large portion of the workin making the floor, which in a preferred embodiment forms part of amore complex modular building unit, can be carried out in a controlledfactory setting. Furthermore, prefabricating certain components of thebuild should increase the efficiency and speed of the build.

In the presently described example, a multistorey building using modularbuilding units can be built faster than with known systems because themodular units can be assembled one atop the other without waiting foreach floor to be completed first. Accordingly, and by way of example,five levels of building units could be assembled in two days while inthat same amount of time two floors of the five levels may be finishedby connecting the floor slabs together through wet joints. The methodallows the construction of the building to be decoupled from the moretime consuming task of pouring concrete and allowing it to dry.

For example, as already described above, during multistorey constructiona precast concrete floor slab in a building unit will be installed abovethe first precast concrete floor slab 10. The upper building unit willbe installed on top of and supported by the upstanding support members(e.g. the temporary support members 103 in some instances or permanentwall/facade structures or columns in other instances, or a combinationof both) provided on the first, lower precast concrete floor slab 10.The installation of the upper precast concrete floor slab above thelower precast concrete floor slab 10 can be carried out before theconcrete beams 13, 15 are poured. In this way the pouring of theconcrete beams 13, 15 is decoupled from the installation of the precastconcrete floor slabs, as the upstanding support members are capable offully supporting the next level of the construction, and indeed arecapable of supporting multiple upper levels (eg. 5 levels) ofconstruction.

The building modules 20, 22, 24, 26 in a preferred embodiment comprisethe precast concrete floor slabs 10, 12, 14, 16 and upright supports inthe form of a facade 21, internal wall structure and/or temporarysupports 103. The building modules could also include location devicesthat guide and correctly locate for attaching an upper module in thecorrect position above a lower module. As shown in co-pendingInternational Patent Application no. PCT/AU2017/050064 the locationdevice may be a cone-shaped locator pin provided on the upright support(which is a temporary tripod support in the embodiment of thatco-pending application) that acts as a dowel and is adapted to locateinto a corresponding recess in an underside of the floor slab or sideattachment (such as a facade) of the building module to be mountedabove. Accordingly, building modules can be correctly positioned oneabove the other in the desired storey configuration without requiringany concrete work to be first completed.

Turning back to FIGS. 4A and 4B, the first beam 32 is parallel to thelong edge 41 of the slab 10. The second beam 34 is parallel to the shortedge 43 of the slab 10. The first beam 32 is positioned at a perimeterof the slab 10. The second beam 34 is positioned at a perimeter of theslab 10. The first beam 32 extends across the entire length of the longedge 41 of the slab 10. The second beam 34 extends across the entirelength of the short edge 43 of the slab 10. The first beam 32 isperpendicular to the second beam 34.

Although the beams have been shown as positioned at a perimeter of theslab 10, it is envisaged that the beams could be offset from theperimeter. In other words, the beams may be inset from a perimeter ofthe slab. In addition, although the beams have been shown as positionedparallel to either the short or long edge of the slab of a module, it isenvisaged that the beams could be positioned at an angle relative to theshort or long edges of the slab.

Referring again to FIGS. 2A to 3B, the precast concrete slab 10 is usedas part of a method of laying a larger floor slab of a building. Thefirst precast concrete slab 10, which is the base of building module 20,is installed on site and a second precast concrete slab, for exampleslab 12 of building module 22, is installed adjacent to and spaced fromthe first precast concrete slab 10. Supporting formwork 23, 39 isprovided in the space 25 between the first and second slabs to form achannel 28 into which concrete for ‘stitching’ can be poured.

The supporting formwork could be provided as a separate structure, suchas the sacrificial or removable formwork 23 as shown in FIG. 1 , or assupporting formwork integrally formed with the precast floor slab, suchas the flange 39 laterally extending from the side of the floor slab asshown in FIGS. 6, 10 (a), 10(b), 11(a), 11(b) and 12.

FIG. 1 illustrates preliminary formwork (bearers) erected at ceilingheight between two adjacently spaced building modules 202, 204, whichwill form the formwork for the floor of the storey above, and fullformwork with board erected at floor level between building modules 202,204, which forms the formwork 23 for the floor between building modules202, 204. Also visible in FIG. 1 are reinforcement bars 27 protrudinginwardly into the space 25 that will form the wet joint connectionbetween the precast floor slabs 102, 104 of modules 202, 204respectively. The reinforcement bars 27 tie together the precast floorslabs 102, 104 with the poured (wet joint) connection once the in situpoured connection is dried. The formwork forms a channel 28 into whichconcrete can be poured.

Concrete is poured into the channel 28 created by the formwork 23 toform a continuous concrete floor between the precast concrete floorslabs or, as shown in the embodiments of the drawings, concrete ispoured to form beam 13 between the first precast concrete slab 10 andthe second precast concrete slab 12. Whether or not a beam is formed,the result is a continuous floor slab 17 of a building 100. The concreteis poured to be level with a top surface of the first and second precastconcrete floor slabs 10, 12. In other words, the poured concrete doesnot form a topping slab that overlays the first and second precastconcrete floor slabs 10, 12 (although this may be performed if desired).The poured concrete beam 13 is angled relative to the integrally formedbeam 32 in the first precast concrete slab 10, thereby forming a two-waytensioned or reinforced slab. In particular, the poured concrete beam 13is perpendicular to integrally formed beam 32.

An alternative embodiment but with similar effect is illustrated inFIGS. 10(a) to 12. In that embodiment adjacent floor slabs 400, 500 areprecast to have flanges 39, or tongues, extending laterally of the sidesof the floor slabs. The flanges of each floor slab are positioned facingeach other with only a small gap 410 left between them, which is filledwith a plastic or silicone filler. The almost abutting flanges 39 arethinner in height/thickness than the height/thickness of the floor slabsand so create a channel 28 where the two adjacent slabs meet. Similar tothe above-described embodiment of the formwork 23 provided as aseparate, non-integral structure, the channel 28 is adapted to be filledwith wet concrete to create an in situ wet joint.

FIGS. 11(a) and 11(b) illustrate in perspective views a first module 20with floor slab 400 that is located against a second module 22 withfloor slab 500 ready for pouring, but before filling gap 410 with afiller. The cross-section diagram of FIG. 12 indicates in dotted linesthe area 420 which will be occupied with in situ poured concrete.Reinforcement tie bars 27 embedded in the floor slabs 400, 500 protrudesideways into the wet joint area 420.

Referring back to FIG. 2A, the completed slab 17 has four precastconcrete slabs 10, 12, 14, 16 and two poured concrete beams 13, 15. Thethickness of the poured concrete beams 13, 15 are substantially equal tothe thickness of the integrally formed precast beam in the precastconcrete slabs 10, 12, 14, 16. In other words the concrete beams 13, 15are poured to a thickness greater than a thickness of the first portion11 of the first concrete floor slab 10. The concrete beams 13, 15 arepoured to a thickness substantially equal to the thickness of the secondportion 101 of the first concrete floor slab 10 (i.e. to a thicknesssubstantially equal to the thickness of the integrally formed concretebeams 34, 37). The precast beams 34 and 37 in precast slabs 10 and 16are co-axial, the precast beams 32 and 33 in precast slabs 10 and 12 areco-axial, and the precast beams 35 and 36 in precast slabs 12 and 14 areco-axial.

Once the poured beams 13, 15 set precast beams 34 and 37 in precastslabs 10 and 16 form a single continuous beam, precast beams 32 and 33in precast slabs 10 and 12 form a single continuous beam, and precastbeams 35 and 36 in precast slabs 12 and 14 form a single continuousbeam. This results in the completed floor slab 17 having five beams intotal, as shown in FIG. 3B, some of which are angled to each other.Specifically, the completed floor slab includes a combination ofperpendicularly aligned precast and poured beams. The single continuousbeams may span the entire length or width of the completed slab 17.

While it is preferable for the poured beams 13, 15 and the integrallyformed beams 32, 33, 34, 35, 36, 37 to have substantially the samethickness, it is envisaged that the poured beams 13, 15 could be thickerthan the integrally formed beams 32, 33, 34, 35, 36, 37, or that theintegrally formed beams 32, 33, 34, 35, 36, 37 could be thicker than thepoured beams 13, 15.

The precast beams are cast with reinforcement tie bars 27 protrudingfrom their side edges that are embedded into the wet in situ joint andassist in tying the precast slabs to the poured connections. The tiebars may be in the form of reinforcement bar, or steel angle cast alongthe edge of a floor slab.

It is envisaged that the building module 20, or the precast concreteslab 10 on its own, could be constructed at a first location, and thenmoved, for example by being transported from the first location to aninstallation location, where the building module is installed. The firstlocation may be a factory or a warehouse where the initial components ofthe first building module 20 may be more easily assembled in an assemblyline fashion, in order to assist in shortening overall constructiontime.

Alternatively, if there is room on the building site, an assembly areamay be located, for example, in an area that is designated as acourtyard in the finished building. In this example the first buildingmodule 20, or the precast concrete slab 10 on its own, can beconstructed on the building site in a designated assembly area beforebeing moved into position, for example by a crane, and installed. Itwill be understood that locating the assembly area, or factory, on thebuilding site will help reduce transportation costs.

It will be understood that by installing the temporary support members103 and the façade 21 before the precast concrete floor slabs are movedinto the installation position the building site can operate withincreased safety. This is because the installation of the outer wallsremoves the live edge of the building site, thereby eliminating a liveedge for workers to fall from. In addition, by removing the live edgethe construction process also becomes more efficient as there is no needfor external barriers to be installed around the building before workerscan enter the worksite.

While the precast concrete slabs 10, 12, 14, 16 are described above asbeing connected by pouring concrete 11 between the modules, additionalsteps can be used to further increase the strength of the finished slab17. Specifically, strengthening can be achieved by use of reinforcementbars or mesh in the wet joint and/or post-tensioning the finished,continuous wet joint/precast combination floor.

Referring now to FIGS. 5 to 9 , a post-tensioning technique isdemonstrated. Two precast slabs, shown as first precast concrete slab 40and second precast concrete slab 50, are connected by poured concrete60. The first precast slab 40 has a bore 42 that extends through thefirst precast slab 40. The bore may be in the form of a cast conduitinto which will be received the tension cable. The bore 42 in the firstprecast slab 40 extends out of opposite ends of the first precast slab40. The second precast slab 50 has a bore 52, or cast conduit, thatextends through the second precast slab 50. The bore 52 in the secondprecast slab 50 extends out of opposite ends of the second precast slab50.

The bores 42, 52 in the first and second precast slabs 40, 50 can beformed using any suitable method. For example, the bores 42, 52 may beformed when casting the precast slabs 40, 50. For example, a conduit(not shown) may be placed in a mould for the precast slab and concretepoured around the conduit so that the conduit is embedded in the precastslab 40, thereby forming a bore in the precast slab 40.

During installation of the precast slabs 40, 50 the first precast slab40 is installed first. The second precast slab 50 is installed adjacentand spaced from the first precast slab. As shown in FIG. 5 , the secondprecast slab 50 is installed so that it is in the same plane as thefirst precast slab 40, regardless whether or not the slabs 40, 50 areelevated. The second precast slab is preferably installed so that thebore 52 in the second precast slab 50 is aligned with the bore in thefirst precast slab 40. More specifically, the second precast slab 50 ispreferably installed so that the bore 52 in the second precast slab 50lies in the same plane as the bore 40 in the first precast slab 40.

A conduit 62 is installed in the formwork between the bore 42 in thefirst precast concrete slab 40 and the bore 52 in the second precastconcrete slab 50 to extend the tensioning passage 64 through both thefirst and second precast concrete slabs 40, 50. Specifically, theconduit 62 is connected to the bore 42 in the first module 40 and thebore 52 in the second module 50, thereby forming a continuous tensioningpassage 64 from one end of the first precast slab 40 to the opposite endof the second precast slab 50.

In other words, the tensioning passage 64 extends the entire way throughboth the first precast slab 40 and the second precast slab 50, allowinga cable to be fed through the tensioning passage 64 such that the cableextends out of an end of the first precast slab 40, and extends out ofan end of the second precast slab 50. The conduit 62 is connected to thebores 42, 52 to form a seal. The seal is fluid tight and prevents theingress of concrete into the tensioning passage 64.

The tensioning passage may be formed in a draped profile, undulatingbetween slabs and at the outer facade edge of the building (as shown inFIG. 6 ) to increase the level of tension achieved by post tensioning.

Concrete 60 is poured to connect the first and second precast slabs 40,50, forming a slab of a building 70. The concrete surrounds the conduit62, thereby embedding the conduit 62 in the poured concrete 60 as wellas the in situ bars protruding from the side edges of the precast floorslabs.

Once the concrete 60 has set a tendon or cable (not shown) is fedthrough the tensioning passage 64 and the cable is tensioned. Tensioningof the cable applies a compressive force to the first precast slab 40,the second precast slab 50, and the concrete 60 connecting first andsecond precast slabs 40, 50. Tensioning the completed slab 70 acts tostrengthen the slab, allowing it to support more weight.

The tensioning process involves fixing one end, the dead end, of thecable using an anchor (not shown) and then pulling the opposite, liveend of the cable using a winch or stressing jack. As shown in FIG. 7 ,the precast panel 140 may have a stressing pocket 144 that the jackstressing machinery sits in to tension the cable. The stressing pocketcan be formed when casting the precast concrete slab by including asacrificial fibreboard or foam block.

Once the slab has been tensioned to stress the concrete floor under thedesired compression the live cable ends are tied and/or grout tubecontaining the cable is filled with high strength grout under pressureto fix the cable in tension.

While the tensioning passage 64 has been described as a single passagein a single direction, it is envisaged that there could be multiplebores in a single precast concrete slab that are used to form multipletensioning passages. These bores could be substantially parallel to eachother to provide tensioning in a single direction, or they could beangled to one and other, for example perpendicular and overlapping, inorder to provide tensioning in two or more directions. Referring to FIG.7 , first precast slab 150 has a first bore 152 and a plurality ofsecond bores 154. The plurality of second bores 154 in the secondprecast slab 150 are substantially perpendicular to the first bore 152.

Referring to FIG. 5 four tensioning passages 65 (made from conduits) areshown in the intermediate concrete connection 60, which are parallel toeach other and perpendicular to the tensioning passage 64 that extendsthrough the first and second precast slabs 40, 50. In addition, whileonly one cable has been described as passing through the tensioningpassage 64, it is envisaged that two or more, three or more, four ormore, or five or more cables could be used in each of the tensioningpassages 64, 65. As shown in FIG. 5 , each tensioning passage 65 hasfour tensioning cables 66.

Referring to FIGS. 8 and 9 , the precast concrete slab 240 has a beam241 and a plurality of bores 242. The bores 242 are located in theprecast beam 241.

It will be understood that the method of post-tensioning two precastconcrete slabs can be used on its own, or in combination with the methodof forming a slab using precast concrete slabs with integrally formedbeams. In other words, while the connection to form a post-tensionedslab has been described with reference to modules having one or moreprecast beams, it will be understood that the method of connectingmodules to form a slab could be applied to modules without precastbeams.

It is also understood that steel reinforcement bars and/or mesh can beused in place of post-tensioning in order to strengthen the completedfloor including the in situ connection between precast floor slabs.

In addition, as described above with reference to the precast concreteslabs 10, 12, 14, 16, the first and second precast concrete slabs 40, 50may form the base of a building module for a modular building. The firstand second precast concrete slabs 40, 50, or any building modules usingthe first and second precast concrete slabs 40, 50 to form the base ofthe building module, may be made offsite, as described above withreference to precast concrete slabs 10, 12, 14, 16 and building modules20, 22, 24, 26.

Referring to FIGS. 1 to 6 , an example of forming a floor slab of amultistorey building will now be described in detail. The process beginsin a warehouse, where steel beams are positioned on a constructionbed/table. Conduits for forming tensioning passages are laid cross waysand overlappingly tied in position. A sacrificial fibreboard block ispositioned to form a stressing pocket. Alternatively, the table may belaid with reinforcement bar instead of tensioning conduits. Anglesand/or tie bars (generally more reinforcement bars) are also aligned toprotrude from the outer edges of what will be the floor slab.

The bed/table has recesses or voids that result in the precast concreteslab 10 being thicker in these areas. These areas of greater thicknessform the integrally formed precast beams 32, 34 when the concrete hasset. The recesses or voids are perpendicular, resulting in perpendicularbeams 32, 34.

Once the table has been prepared concrete is poured to form a precastconcrete slab 10 that forms a floor of a building module 20. Thisprocess embeds the conduits and/or reinforcement bar into the precastconcrete slab 10 and creates beams that are integrally formed with theprecast concrete slab 10. The steel beams are also partially embedded inthe concrete slab, which add rigidity to the precast concrete slab 10.

Once the concrete slab has set the precast concrete slab 10 is removedfrom the construction bed/table. The precast concrete slab 10 is used toform a building module for a modular building. This can involveinstalling support structures, walls, fixtures and fittings, as desired.

Once the building module has been completed to the desired state thefirst building module 20 is transported from the warehouse to aninstallation location, such as a building site. The first buildingmodule 20 is then installed at the building site (either on the groundfloor or above another building module already installed.

Aside from the ground level modules, installation will involve thebuilding modules being craned and assembled in storeys, with the precastfloor slabs of each module suspended above the floor below.

Once the first building module 20 has been installed a second buildingmodule 22 is installed spaced adjacent to the first building module. Thesecond building module 22 is manufactured and assembled in warehouse ina similar way to the first building module 20. The second buildingmodule 22 also has precast concrete beams 33, 35 and bores fortensioning cables. The second building module 22 is positioned so thatthe integrally formed beam 33 in the second precast concrete slab 12 isparallel and in the same plane as the integrally formed beam 32 in thefirst precast concrete slab 10. The second building module 22 is alsopositioned so that at least one bore in the second precast concrete slab12 is aligned, and in the same plane as, at least one bore in the firstprecast concrete slab 10.

Once the first and second building modules 20, 22 have been installedformwork is either erected in the space between the modules 20 and 22,or is already provided as an integrally extending flange of the module.In the embodiment illustrated in FIG. 1 the formwork is made fromsacrificial fibreboard or the like to take the desired form of thefinished connection. This could be in the form of a poured beam, asdescribed above, or a simple level connection between the precast slabs10 and 12 that continues in the same plane as the precast slabs.

If using post-tensioning, a conduit is installed between the alignedbores in the first and second precast concrete slabs 10, 12 to form atensioning passage that extends through both the first and secondprecast concrete slabs 10, 12.

A concrete beam, or simple connection, is then poured between the firstand second precast concrete slabs 10, 12 to connect the first and secondprecast slabs 10, 12. This process forms a completed slab. The pouredconcrete beam surrounds the conduit connecting the aligned bores,thereby embedding the conduit in the poured beam. Once the poured beamsets the precast beams 32 and 33 form a single continuous beam. Thepoured beam is perpendicular to the continuous beam (made from theprecast beams 32 and 33) that it creates.

Once the concrete beam has set four tensioning cables are fed throughthe tensioning passage so that the cables extend out of the firstprecast concrete slab and the second precast concrete slab. The end ofthe cables that extend from the second pre-cast slab 12 are fixed to thesecond pre-cast slab 12. The ends of the cables that extend from thefirst pre-cast slab 10 extend into the stressing pocket in the firstprecast slab 10. A stressing jack is used to tension the cables. Oncethe cables have been tensioned excess cable is cut off and the stressingpocket in the first precast slab 10 is filled with concrete to form aflat upper surface and to hide the cables.

While feeding the cable through the tensioning passage has beendescribed as occurring after the concrete beam has been poured and hasset, it is envisaged that the cable could be fed through the tensioningpassage any time after the conduit between the aligned bores has beeninstalled.

While the methods above have only been discussed in relation to twoslabs connected side-by-side, or four slabs in a 2×2 configuration, itis envisaged that multiple other configurations could also be created.For example, the slabs may be configured in a 2×1 configuration, a 2×3configuration, a 2×4 configuration, a 3×4 configuration etc. Forexample, FIG. 8 illustrates three precast concrete slabs 240, 250, 270side-by-side.

Precast slab 240 has a precast beam 241. The three precast slabs 240,250, 270 are connected together by poured concrete beams 260, 280. Theprecast slab 240 has a plurality of bores 242 for receiving a tensioningcable. Precast slab 270 is connected to a precast outer wall 280.

As shown in FIG. 9 , the precast slabs, such as slab 240, may be castwith a perimeter, or partial perimeter, of prefabricated channel (PFC)271 which adds rigidity and strength to the slab. The PFC may also takepart in the side attachment of wall structures, such as facades.Alternatively, other fixing means such as brackets may be provided onthe slab for side attachment of wall structures. It is understood theslab may be sufficiently stable during construction to not require anyPFC.

The method described herein may also include vertically inserting apre-fabricated concrete wall panel in between the adjacently spacedprecast floor slabs. FIG. 7 illustrates a lower precast wall panel 170inserted below and between precast floor slabs 140 and 150. In situconnection 160 is formed between slabs 140 and 150 and contains tensionconduits 162, 165 extending in perpendicular directions. As discussedbelow, connection 160 can be cast to tie into the upper end of lowerwall panel 170. An upper precast wall panel 172 is positioned on top ofconnection 160, with lower panel 170 bearing the weight of upper panel172.

Pre-fabricated wall panels are also described in the abovementionedco-pending International Patent Application titled “METHODS ANDAPPARATUS FOR CONSTRUCTING MULTI-STOREY BUILDINGS”, and which alsoclaims priority from Australian provisional application no. 2016902460filed on 23 Jun. 2016, and from Australian provisional application no.2016903025 filed on 1 Aug. 2016 and titled “METHOD FOR CONSTRUCTING ACONCRETE FLOOR IN A MULTISTOREY BUILDING”.

The wall panel can be lowered in position by crane and forms structuralsupport for the building. The wall panels are tied at an upper end tothe precast floor slabs and formwork provided around the wall panel andbetween the floor slabs, as required, along the length of the upper endof the wall panel. Concrete can then be poured into the formwork to forma wet joint to finish the floor and incorporating the wall panel on anunderside of the floor including any tie bars.

It is to be understood that, if any prior art publication is referred toherein, such reference does not constitute an admission that thepublication forms a part of the common general knowledge in the art, inAustralia or any other country.

In the claims which follow and in the preceding description of theinvention, except where the context requires otherwise due to expresslanguage or necessary implication, the word “comprise” or variationssuch as “comprises” or “comprising” is used in an inclusive sense, i.e.to specify the presence of the stated features but not to preclude thepresence or addition of further features in various embodiments of theinvention.

1. A building module used for constructing a modular multi-storeybuilding, the building module being fabricated at an off-site locationto an installation location, the building module comprising a precastconcrete floor and a permanent outer wall fixed at a side edge of thefloor so that the outer wall is suspended by the concrete floor toextend vertically upward and defines part of a façade of the building;the outer wall being suspended by the floor to extend laterally andupwardly from the side edge of the floor by a connection partiallyembedded along the side edge such that the connection bears the load ofthe outer wall at the side edge during transportation from the off-sitelocation to the installation location; wherein when the building moduleis installed at the installation location, the outer wall forms anexternal safety barrier.
 2. The building module claimed in claim 1,wherein the connection comprises a bracket of the outer wall connectedto a fixing joint embedded along the side edge of the floor.
 3. Thebuilding module claimed in claim 1, wherein one or more temporarysupport members are fixed onto the floor.
 4. The building module claimedin claim 3, wherein the temporary support member is configured tovertically support at least part of a further building module above thebuilding module at the installation location until the further buildingmodule is connected to a permanent support structure that supports thefurther building module, whereafter the temporary support member isremoved.
 5. The building module claimed in claim 4, wherein thetemporary support member has a tripod support structure.
 6. The buildingmodule claimed in claim 3, wherein the temporary support member includesa locator provided on the temporary support member to assist incorrectly locating the further building module above the buildingmodule.
 7. The building module claimed in claim 1, wherein the precastconcrete floor is a concrete slab precast with reinforcement.
 8. Thebuilding module claimed in claim 1, wherein the precast concrete flooris a concrete slab precast with integrally formed concrete beams.
 9. Amethod of constructing a multistorey building, the method including:pre-fabricating a first building module off-site, the first buildingmodule having a precast concrete floor and a permanent outer wall fixedat a side edge of the floor so that the outer wall is suspended by theconcrete floor to extend vertically upward and defines part of a facadeof the building; the outer wall being suspended by the floor to extendlaterally and upwardly from the side edge of the floor by a connectionpartially embedded along the side edge such that the connection bearsthe load of the outer wall at the side edge during transportation fromthe off-site location to the installation location; transporting thefirst building module assembled with the outer wall to the installationlocation; and placing the first building module by crane on top of analready installed second building module so that the outer wall of thefirst building module aligns above an outer wall of the second buildingmodule, whereby the outer walls of the first and second building modulesform external safety barriers.
 10. The method claimed in claim 9,including installing a third building module adjacent to the firstbuilding module.
 11. The method claimed in claim 9, including supportingthe first building module above the second building module withtemporary support members fixed to the concrete floor of the secondbuilding module.
 12. The method claimed in claim 11, includingconnecting the first building module to a permanent support structurebetween the first and second building modules to vertically support thefirst building module above the second building module, and removing thetemporary support members.
 13. The method claimed in claim 12, includingsupporting the first building module above the second building modulewith a permanent support member mounted between the first and secondbuilding modules.
 14. The method claimed in claim 11, includingsupporting multiple levels of building modules above the second buildingmodule by way of temporary support members before connecting themultiple levels of building modules to permanent support structures,whereafter the temporary support members are removed.